Browsing by Author "Sabrieva S."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    PREPARATION AND CHARACTERIZATION OF CERAMIC MEMBRANES ON THE BASE OF HALLOYSITE CLAY AND LIMESTONE
    (2020-01-01) Yoleva A.; Djambazov S.; Sabrieva S.
    The development of ceramic membranes based on natural raw materials such as kaolins, clays, zeolites, lime-stones, dolomites, feldspars, quartzs and others appears an efficient solution to purification of water at a low cost. The ceramic membranes are prepared in the form of disks of a size of 3,0 cm x 0,4 cm by dry pressing of a homog-enized batch from halloysite clay and limestone of different quantities at pressure of 50 MPa. They are fired for 2 h at 1100°C. The properties of the sintered ceramic membranes such as shrinkage, water absorption, an apparent density, an apparent porosity and a mechanical bending strength are determined by standard methods. Mercury porosimetry is used to determine the pore size distribution and the average pores size. The phase composition is identified by XRD analysis. The microstructure is observed using SEM. The increase of the limestone content results in an increase of the water absorption and the apparent porosity and a decrease of the shrinkage, the apparent den-sity and the compressive strength. The average pore size equals 2,32 µm, while the total porosity amounts to 45,00 % for the ceramic membrane containing 60 wt.% of halloysite clay and 30 wt.% of limestone. The main crystalline phases found in the sintered ceramic samples refer to anorthite (CaO.Al2O2.2SiO2) gehlenite (2CaO.Al2O3.SiO2) mullite (2Al2O3.SiO2) and wollastonite (CaO.SiO2).
  • No Thumbnail Available
    Item
    STUDY ON THE PREPARATION OF CERAMIC MEMBRANES BASED ON NATURAL AND WASTE MATERIALS
    (2020-01-01) Yoleva А.; Djambazov S.; Sabrieva S.; Gigova A.
    The production of low cost ceramic membranes has been studied by many researchers using a variety of natural raw materials such as clays, kaolins, limestones, dolomites, zeolites, diatomites and various kinds of wastes such as fly ash, sawdust, sewage sludge, bagasse, waste glass, ceramic scrap, etc., modifying the membranes microstructure with the aim to improve their surface porosity, pore size, pore distribution and mechanical strength. Compositions of ceramic membranes containing halloysite clay, limestone and waste diatomite from the brewery industry are prepared. The change of the ceramic membranes properties varying the presence of halloysite clay and diatomite is followed. The ceramic membranes studied are prepared by dry pressing at 50 MPa and sintering at 1100°C within 2 h. The water absorption, the apparent density, the apparent porosity, the mechanical bending strength and the shrinkage of the ceramic membranes obtained are determined. The water absorption and the apparent porosity increase, while the apparent density and the mechanical bending strength decrease with an increase of the waste diatomite content and a decrease of halloysite clay presence in the ceramic membrane compositions. XRD and SEM are used to identify the phase composition and the microstructure. The average pore size of the ceramic membranes studied is determined by mercury porosimetry